function fib:
    &(Number) => Number
    &(n) =>
        if ((n = 0) or (n = 1)):
            1,
        else:
            let (a,b) := parallel ({ fib (n -! 1) }, { fib (n -! 2) }),
            (a + b);

entry
    { sys::println { fib 30 }.{String} }
        . { crash-on-error };

